Colossal Storm Rages Over Saturn’s Surface

The largest storm seen on Saturn in more than 21 years has now been encircling the planet for a record-breaking 200 days.

First appearing as a tiny blemish on Dec. 5, 2010, the storm is still going strong today, surpassing the ringed giant's previous longest tempest, which lasted 150 days back in 1903. NASA’s Cassini spacecraft, in orbit around Saturn, has given astronomers a front-seat view of this enormous maelstrom and provided valuable data.

From its humble beginnings, the storm has grown to engulf the entire area between Saturn’s 30th and 51st north latitudes. From north to south, the tempest stretches about 9,000 miles — greater than diameter of the Earth — and covers two billion square miles, or eight times the surface area of our planet.

Above:

Northern Shower

The storm marches through the planet's atmosphere in the top right of this false-color mosaic from Cassini. Red and orange colors in this view indicate clouds that are deep in the atmosphere. Yellow and green colors, most noticeable along the top edge of the view, indicate intermediate clouds. White and blue indicate high clouds and haze. The rings appear as a thin horizontal line of bright blue.

Storm's Birth

Cassini's radio and plasma wave science instrument first detected the lightning radio signals associated with this storm on Dec. 5, 2010.

The tempest is visible as a spot on the terminator between night and day in the northern hemisphere. The spot appears slightly brighter than the surrounding clouds in an area about two-thirds of the way north of the equator. At this time, it measured only 1,100 miles east-to-west and 800 miles north-to-south.

The Growing Storm

The earliest image of the storm, taken Dec. 5, 2010, is in the top left of the panel. The storm appears only as a small, white cloud on the terminator between the day side and night side of the planet.

The next view, in the top middle of the panel and taken Jan. 2, 2011, shows that the head quickly grew much larger and a tail began to trail a great distance eastward. By the April 22 image, in the bottom left of the panel, the tail is south of the head and is well established by this time.

Between the time of the May 18 image and the next image shown here — from Aug. 12 — the head of the storm was engulfed by the part of the storm’s tail that spread eastward at the same latitude as the head. The Aug. 12 image, in the bottom right, shows that the head has lost its distinct identity and is now just part of the jumble of the storm.

True Colors

This mosaic shows the storm’s effects encircling the planet and was created using 126 images taken in succession as different parts of Saturn’s northern hemisphere rotated into Cassini’s view.

Images taken using red, green and blue spectral filters are usually combined to create a natural color view. Because visible red light images were not available, images taken using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers were used in place of red. So the color is close to natural color, but is not exact.

The head of the storm is near the center, and a train of vortexes appears as blue spots just to the south of the head. These blue spots are parts of the storm’s tail that have already encircled the planet and are approaching from the west. The blue color indicates they have some high, semi-transparent haze but no thick clouds underneath because there are no white or yellow colored clouds shown here.

The Whole Storm

Seen here is a part of the storm when it was already encircling the entire planet. At the head of storm the clouds at different heights crisscross each other. The red color shows deep clouds with no towering tops. These clouds, visible as bright red at the northern part of the storm, are very interesting to scientists who study wind shear, or the speeds of clouds at different altitudes. The wind shear is depicted in the different colors in these areas.

The blue oval area on the far right is a hole in the deep clouds of the atmosphere. Data from Cassini's composite infrared spectrometer show this blue area is a cold spot in the stratosphere. The blue color means it is high haze, but underneath there are no deep, or lower, clouds because there is no red color here. White and yellow colors at the head of the storm show these are high, thick clouds characteristic of convection and the solid anvils of towering thunder storms.

Click the link below to see the entire storm around Saturn from head to tail.

Storm Head

The head of Saturn’s huge northern storm is well established in this view captured early in the storm’s development by NASA’s Cassini spacecraft in late 2010.

Saturn’s atmosphere and its rings are shown here in a false color composite made from three images taken in near infrared light through filters that are sensitive to varying degrees of methane absorption. Red and orange colors in this view indicate clouds that are deep in the atmosphere. Yellow and green colors, most noticeable near the top of the view, indicate intermediate clouds. White and blue indicate high clouds and haze.

Rainbows in the Storm

Eleven Hours

These two natural color views taken 11 hours — one Saturn day — apart by NASA’s Cassini spacecraft help scientists measure wind speeds in the huge storm seen here in the planet’s northern hemisphere.

The view on the left is earlier than the view on the right. Scientists use these time-lapse images to track specific, small, and sometimes subtle features in the clouds. The smallest features visible in the image are the most useful. However, tracking the clouds in this storm is difficult because the features don’t always last one Saturn day.